Nuclear piles



" 4.1. BATHI'AL Il" 4 .NucLEAR lPima; 7

sheets-sheet 1 Y Filed July' 5, 19s@ nvenlors The present invention -relates to' internal-boilingpuclear piles, and has for an object improvements therein.

ln internal-boiling nuclear piles, the liuid delivered to the exterior thereof is generally composed of an emulsion ofwater and steam.

It is a more particular object of the invention to provide a novel pile which, in particular, allows drying' and super-heating of the saturated steamin the interior of the pile.:

The invention provides yan internal-boiling nuclear pile,

comprising hollow cylindrical vfuel elements whose, irlternal bore constitutes a coolant chan-nel, thesaid elements comprising a lower portion: where the boiling of Seite im@ Edouard Roche, Paris, France, as sign- Y the evacuation of theunvapourised water and the equalithe coolantA takes place,`l an intermediate portion wherethe liquid phase is separated from the vapour phase of the coolant,'and an upper portion where the coolant vapour is super-heated, a moderator locatedoutside said fuel elements, said coolant and said moderator consisting of water, hermetic closure measin the moderator' regionl at a levellocated immediately above said intermediate portion of said elements in order to define a lower region in-which the moderator surrounds said lower portion of thev fuel elements and an upper regionin which the moderator surrounds said upper portion of the fuel elements, means for admitting -cold water into said upper region, means for slightly heating said Vcold water in said upper region, and external conduits for passing' `the slightly heatedwater 'by gravity from said upper region into said lower region, means for further heatingof: said water in said lower region, means for admitting the thus further heated water to the bottom of the said coolant channel,

so `that said water is partially vapourisedin said lower portion of the fuel elements, means for evacuating the vapourised water into the said intermediatev portion and means causingtthe dry vapour torise into --the said upper portion for super-heating.

Good thermal contact must be realised between the coolant and the fuel and the latter must be thermally isolated as well as possible from the moderator. The cooling channels are steam-generators in their lower part and steam super-heaters in their upper part.

In order that-the invention-may be morclearly understood, reference will now be made to the accompanying drawings which .schematically showone embodiment thereof by way of example, and in which:

FIGURE 1 shows an axial section through part of a pile according to the invention, l

FIGURE 2 shows a cross-section through one form of 'fuelelement for use in the pile of FIGURE l, and

form of fuel element.

The pile according to the invention, shown in FIGURE 1, comprises a chamber, part of which is shownl as 1, and carries horizontally a plate 2, -of a material which does not absorb neutrons, separating the super-heating zone 3 and the boiling'zone 4. This plate 2 comprises labyrinths 5`al1owing the Apassage of the fuel elements an constituting hermetic sealing means. The fuel elementsl are shown schematically in FIGURE l, and comprise a supporting part 6 serving for the pos'- tioning of the elements, permitting the entry of the cool.- ing water and ensuring the union between the covers 7 FIGURE 3 shows a cross-section through anotherv ,fa-ce antenas Patented Jan.- 18, 1963 t, `a t and8enveloping thefuel, The fuel elements .may be supported in known' vfashion by a perforated plate P which receives the supporting part 6 .-and is secured to the wa'll of chamber 1 in any desired fashion. The fuel elements also have a, vapourisation fuel fpart 9 g with an interior channel 10 serving for thepassage of 4the cooling water, forced into rotation by the -system' of helicoidal ribszllan intermediate part 12 comprisingparts 13 vfor sation of the vapour pressures; a 'super-heating fuel part 14 similar to the evaporation vfuel part, but capable Aof being o f smaller` diameter; and a terminal part 15 not` con-taining any fuel intended to separate the c old moderator zone from the super-heated steam zone and further portion of the tlux which super-heatsthe steam, and it.

serves as themoderatorfor the super-heating part. Then itleaves-through an outlet 18 to enter into lthe zone 4 through several valves or gates shown schematically at 19, assuring the maintenance of the level 20 in the boiling zone of the pile; it is heated during its descent around the fuel elements, without or with a very small production of steam which would pass through the equilibrium ports 13.

The water then enters yinto the channel 10 where it is partially vapourised, the unvapourised leaving through the ports13, whilst the dry steam goes on to be superv"heated in the part 14 and toleave the pile at 2l.

lIt'is known that an auto-regulation of the piles can be `obtained by a subfcooling of the feed water in the case of an increase in the power required; in `order to utilise. this autoregulation in the pile, the feed water can be divided into two parts: one part passing, as has just been described, to the moderating zone of the superheating part 3 and maintaining a constant level (equilibrium ofleaks and systematic losses) in the `zone 4, and another partv being directed to various parts of the modi form of aring divided into three parts 23 with a gap 24 between each for expansion. The fuel is forced against the cover 7 by bearing against the cover 8.

The supporting of the parts 23 of uranium oxide on the exterior cover 8 is obtained in two different ways in these two gures.

In FIGUREZ, the calcined uranium elements have In FIGURE 3, the uranium oxide elements `are portions 26 of a cylinder and do not have any stumps, the spacing of the fuel element from the exterior cover being ensured by several longitudinal blades 27 integral with the cxterior cover 8.

In the two cases, the spaces between theexterior cover and the fuel element can, according to the case, be filled with non-absorbent bodies 28, for example of magnesia, to provide thermal isolation, or they can be leftempty.

In a particular case, an operating calculation with a fuel element of 3 mm. thickness and' an isolating zone of scrapes mm. of magnesia, has shown that, for a heat fluir of` lo@ isn/ctn.2l on the interor'covenheld at 300? C. by the.'

production of steam with super-heating,v the extreme temperaturesof-th'e uranium oxide will be of the order of 550 C. and 1050 C.,l and that the heat flux passing 'tlirouglrthe exterior 'coverheld at 200 C. will only be 4 aL/cm?. This calculation has b een made in the case a cartridge filled with a' gas having the conductivity ,of l'carbon dioxide gas.' With la' cartridge lfilled withl helium, the interior equilibrium'temperatures lwill be iov/ered and the vproportion of lthe heat'flux between the interior and 4the exterior will be lowered a little.` I

We elaii'rr: .l

l. An internal-boiling nuclear pile comprising hollowl `rylindrica'l fuel elements whose inter-nal bore V'constitutes coolant `channel,"the said 'elements comprising a 'lower v v portion where the boiling of'thecoolantta'ke's place-an intermediateportion whereathe liquid phase is Separated from the vapour phase ofthe coolant, and an upper portion where the coolant vapour is super-heated, a mod'e`r" ator located outside said fuel elements,isaid"cool-ant and said moderator 'consisting of water, hermetic closure means in the moderator region at a level located immediately above said intermediate portion of said elements ,in'order to define a lower region in which the moderatorV surrounds said lower portion of the fuel elements and anl upper `'region in which the moderatorsurrounds said 'upper portion of the rfuel elements, means foradmitting cold water into said upper region; means for Aslightly .heating said Coldwater in said upper region,l and external conduits' for passing the slightly heated ,water by lgravity :from said upper region into said lower region, means for further heating ofv said water in said lower region, means for admitting the thus further heated water to-the bottom of the said 'coolant channel, so thatsaid water is partiallfy vapourised in said lower portion of the. fuel elements, means for evacua'tng the vapourised water into the said intermediate portion and means causing the dry i vapour toA rise into the said upper portion for super-heating..

2.y Atrinternal-boiling' nuclear pile comprising a cham- .b er, a plate ofv amaterial which does not absorb neutrons Aseparating' said 'Chamber' into up'p'er andlower regions,

sealing means in vsaid plate,'hollowcylindrical yfuel Aelements, internal'helical ribs in said fuel elements consti- I tuting a ycoolant channel-,ysaid fuel elements passingl .through said sealing means and comprising, below said plate, a lower portionwhere' the coolant is vapour'ised and an. Airltei'r-nediate"portion,having'openings for A'evacuation of Ithe liquidphase vof the coolant which is given a rotary movement by said helical ribs, land to equalise the .vapour .v pressures', between theinsidev andthe outside of Asaid fuel ,elemenl and -above said platee an upper portion where the coolant vapour is si1per-hea`ted,fuel-element-supporting means; i-n the said `lower portion of said chamber,-

. No references cited. I 

1. AN INTERNAL-BOILING NUCLEAR PILE COMPRISING HOLLOW CYLINDRICAL FUEL ELEMENTS WHOSE INTERNAL BORE CONSTITUTES A COOLANT CHANNEL, THE SAID ELEMENTS COMPRISING A LOWER PORTION WHERE THE BOILING OF THE COOLANT TAKES PLACE, AN INTERMEDIATE PORTION WHERE THE LIQUID PHASE IS SEPARATED FROM THE VAPOUR PHASE OF THE COOLANT, AND AN UPPER PORTION WHERE THE COOLANT VAPOUR IS SUPER-HEATED, A MODERATOR LOCATED OUTSIDE SAID FUEL ELEMENTS, SAID COOLANT AND SAID MODERATOR CONSISTING OF WATER, HERMETIC CLOSURE MEANS IN THE MODERATOR REGION AT A LEVEL LOCATED IMMEDIATELY ABOVE SAID INTERMEDIATE PORTION OF SAID ELEMENTS IN ORDER TO DEFINE A LOWER REGION IN WHICH THE MODERATOR SURROUNDS SAID LOWER PORTION OF THE FUEL ELEMENTS AND AN UPPER REGION IN WHICH THE MODERATOR SURROUNDS SAID UPPER PORTION OF THE FUEL ELEMENTS, MEANS FOR ADMITTING COLD WATER INTO SAID UPPER REGION, MEANS FOR SLIGHTLY HEATING SAID COLD WATER IN SAID UPPER REGION, AND EXTERNAL CONDUITS FOR PASSING THE SLIGHTLY HEATED WATER BY GRAVITY FROM SAID UPPER REGION INTO SAID LOWER REGION, MEANS FOR FURTHER HEATING OF SAID WATER IN SAID LOWER REGION, MEANS FOR ADMITTING THE THUS FURTHER HEATED WATER TO THE BOTTOM 